Various rechargeable batteries have been put into practical use as a power source for mobile electric devices, such as a cell phone and a laptop computer. Especially, a lithium-ion secondary battery which is lightweight and which has a high voltage and a large capacity, and an electrical double layer capacitor having excellent charge/discharge rate characteristics have been widely used.
A battery used as power supply for vehicle and others needs to discharge and charge a large current in a short time upon starting and stopping the car, but the conventional battery has a high internal resistance so that it cannot exhibit practically satisfactory high-rate charge/discharge cycle characteristics. In addition, the conventional battery is unsatisfactory in respect of the charge/discharge capacity from the viewpoint of the running distance, and further unsatisfactory in respect of the adhesion properties between the electrode active material layer and the metal current collector from the viewpoint of the safety.
One of the reasons why the battery cannot exhibit satisfactory properties as mentioned above resides in that the resistance between the metal current collector and the active material layer is so high, while the adhesion force between the metal current collector and the active material layer is not satisfactory.
As a method for solving the above problem, a method has been proposed in which a metal current collector is provided with a conductive coating layer, and an active material layer is formed on the surface of the conductive coating layer to reduce the resistance at the interface between the metal current collector and the active material layer, thus improving the adhesion force between the metal current collector and the active material layer (patent documents 1 and 2).
Especially, a method using, as a binder, polyvinyl alcohol modified with a silanol group, which is capable of being chemically bonded to a hydroxyl group on the surface of a metal current collector as shown in the following formula (A):

wherein R10 is H or —COCH3, and each of R11 and R12 is H or an ethyl group, has been proposed (patent documents 3 and 4).
Further, a method has been proposed in which the surface of a current collector is preliminarily treated using, e.g., a silane coupling agent and coated with a conductive composition for coating a current collector for a battery or an electrical double layer capacitor (patent document 5).
For solving the above problem, the present inventor has made a method using a conductive composition for coating a current collector for a battery or an electrical double layer capacitor wherein the conductive composition comprises polyvinyl alcohol, a silane coupling agent, a polycarboxylic acid which fauns a bond with a hydroxyl group of the surface of a metal current collector and of the polyvinyl alcohol, and with a silanol group of the silane coupling agent, and bonds them together through an ester linkage, and a conductive auxiliary (patent document 6).